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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 01-22-2011, 01:35 PM   #61
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^if you remove your airbox you should see the alternator label. I'd go for a new Valeo. carries new 120A alternators.
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Old 01-22-2011, 01:44 PM   #62
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Thanks for your post and photos too, it has inspired me to take on the job.
After following this thread I'm ready to replace the VR (Valeo) on my '03 325xi wagon (auto).
Please confirm if this can be done without removing the alternator?
Where is the best place to source the part, should I look for new, rebuilt or salvage?
This is my first shot at this type of repair so any other advice is welcome, thanks. D
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Old 01-22-2011, 01:45 PM   #63
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So far so good thanks.
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Old 02-16-2011, 06:17 AM   #64
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Follow up, I've replaced the VR but now the engine wont start, I've charged the battery and she cranks but doesn't turn over. Any thoughts?
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Old 02-16-2011, 06:40 PM   #65
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Thanks I did the same but now am having starting problems, she cranks but doesn't turn over. I replaced a Valeo VR which, did "click" (as another post pointed out) in so I'm wondering if there is something else in the area that I might have unknowingly disconnected while working on it?? Any thoughts? Thanks.
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Old 02-22-2011, 02:16 PM   #66
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determining which alt you have

Originally Posted by Girmis View Post
I got this question:
Saw that you pulled your alternator. Is there any way to tell from the top if it's a Bosch or Valeo?

The answer:
Yes, you can, but you will need a mirror and a light. There is a sticker on the black plastic back plate (you can see that in the first picture - it looks like some bar code). It is faint on my alternator, but it is readable. I would suggest removing air filter housing (easy - 2 10mm bolts). You might be able to see even without taking it out, but it will be very very hard to get down to alternator ....
I'm having voltage issues in my 6/03 ZHP. After reading this thread and another (, I figure the likely culprit is the VR.

In terms of preparation, I wanted to know which alternator I have so that I can buy the correct VR, without removing either one. I used a telescoping mirror and shot the following photo of the sticker on the back of the alternator (VR cover?). The only thing I removed is the air filter box.

Ran a search on the number in the bottom of the pic (0124515105) and it turns out that's the Bosch part number for the 120A alternator.

Note to those who like me who cannot see this label without a mirror: I shot the pic on iPhone, flash off, then used Preview on a Mac (not iPhoto) to make a mirror image of the photo so that I could read the numbers more easily.
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Old 04-02-2011, 12:57 PM   #67
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VR leads are both 9mm long

I have alternator/VR issue with my car as well. 120A Bosch in a 2002 330i with 73K miles.

I got the alternator tested at Autozone and it failed. Return home, and pulled out the VR to see if the contacts are worn out, and it turns out that they are not - both are 9 mm long.

The alternator bearings are good as well, and the pulley axis turns smoothly without a squeak.

From what I've read in these forums, most of the time the problem is with the regulator, and those who have posted have invariably seen that the contacts are worn out.

I am planning to order a new VR today, but before I do that... is there anything else I should check alternator for, aside from the smooth rotation of the pulley axis indicating good bearings?

Thanks in advance for your help!

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Old 04-08-2011, 01:53 AM   #68
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Alright... I ended up replacing the alternator as well after old Bosch alternator paired with new regulator (removed from new Autozone alternator) resulted in failure on Autozone's and Kragen's tester.

I don't know how much stock to put in Autozone/Oreilly testing (because the persons testing the alternators at these locations also initially showed the new alternator paired with new regulator to have failed in their testers. The Autozone guy was eventually able to show that the new alternator I had purchased from them, actually passing in their tester.)

Now that I have the alternator installed, and the car is back on the road again, I'm noticing a slight wheezing sound that seems to be coming from the alternator. I know it's not the belts or pulleys , as I replaced them with genuine OEM parts just a couple of months ago.

1) Has anyone else using the Duralast alternator experienced a slightly different sound (compared to when Bosch/Valeo alternator was installed) from their car when engine is revved?

2) Those who have a Duralast alternator installed... what has been your experience thus far in terms of durability? I know that Autozone gives Lifetime Warranty, but I'd rather not open the car apart to replace yet another alternator.

Thanks in advance!

2002 330i
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Old 04-10-2011, 09:24 PM   #69
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Alternator noise at 1000 rpm

Can a failing voltage regulator cause excessively loud noise only at a certain rpm, let say 1000rpm? I have been hearing this alternator noise/whine at 1000rpm all the time. I replaced the alternator with a refurbished once last year and the noise is still there. Some mechanics said it's normal sound when the alternator recharges. Why do I only hear it at 1000rpm? The pitch is quite high and I find it really annoying. I have looked into the possibility of vacuum leak and concluded that that's not the reason. Any insight would be appreciated.
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Old 05-18-2011, 11:56 AM   #70
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Originally Posted by BMW_E46_SA View Post
Hi Everyone, I own a 2003 E46 318i (N42 valvetronic) with 125 000 km.

I hope someone could help me a bit. I have been having this problem for the last 6 months or so.
My alternator lights comes on for a second or so togther with the a drop in revs and a jerk.
I have replaced my battery, still the problem exists.
I have recently reconditioned my alternator, so new Regulator, new pulley, new bearings. But still the problem exists.
But I must say the IDLE is alot smoother now.

I also had my car hooked up for Diagnostics , it states that Cylinders 1 and 2 are running at 60% effeciency.
So now I'm not sure if the engine is cutting off for some other reason which causes the alternator to stop spinning
for a short while which lights up the alternator light.

Or the alternator core is dying causing the alternator to behave erratically.

Currently on idle my alternator pushes out 14,3v but after driving around a while it drops to 13,3v.
And the problem always happens after driving around for 20 minutes or so when the engine is hot.
So it's possible the core is dying once it gets hot.

But the strange part is that after it jerks and the light come on for that second, then on most occassions it's fine for th rest of the journey.
Several times it stwitched off at the traffic lights. But starts up fine again.

It seems like if the REVs are high enough it does switch off but kicks itself into life but with REVS low like at the traffic lights it can't kick itself, so it stalls.

Does any of this make sense. I really don't want to spend more money on a new alternator if it doesn't solve the problem.

Any help would be appreciated greatly.

Can the alternator die just for a second or so, just enough to stop energy to the plugs which causes the jerk or

is it possible the engine cylinders 1 or 2 cutoff due to bad plug etc, causing a stall or jerk which also causes the alternator light to flash ?

Does the voltage drop on the alternators when it gets hot ?
How low can the voltage go before it causes problems ?

You would think that if the alternator voltage drops below a certain point for a second or so that the battery could provide the energy required without the engine missing a beat.
i own a 2002 316i "n40b16i" 88000 KM
i have experienced exactly the same problem.
At first and car serviced addressed the problem as voltage regulator but it did not solve the problem and i stalled on the way back to home. I have had to leave the car on some neighborhood i do not know.
Next day when we connect the car to the computer the diagnosed the problem as crank sensor and we replaced it.
The problem is gone.
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Old 05-18-2011, 08:52 PM   #71
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how did you get it for $53. i just looked on the website and it was $135!!!
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Old 05-19-2011, 06:18 PM   #72
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I bought a new Bosch voltage regulator from AutohausAZ last week for $40 (for the Bosch 120A alternator.) Price may differ depending on which alternator you have.
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Old 05-27-2011, 01:15 PM   #73
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Just want to say thanks to this thread. changed voltage regulator and solved alternator problem on my car. didn't need to take off alternator.
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Old 05-30-2011, 11:08 PM   #74
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Unhappy Voltage Regulator Issues

Thanks for the great post. I followed it step-by-step and now my electrical issue is WORSE! I'm no slouch when it comes to things electrical OR mechanical so I'm a little confused about what the issue is.

I've got the Bosch 120A alternator (just like in the pictures!) and I've had an intermittent battery light that's been getting worse. I swapped out the VR and now I've got a constant battery light. The cluster is now showing 11.8V constantly instead of 13.8 with the occasional flash of 12.4. I KNOW I made all the connections and snugged them up tight. The VR replacement is pretty much goof-proof. How could it be worse? Did I get a bad VR? Should I just bite the bullet and get a new alternator or does anyone have any ideas?

I REALLY don't want to do this again, much less a third time! I know I've got to take it out again so I'm going to take the ALT to a parts store for testing. If it test good, what then?

THANK YOU in advance for any ideas and help you may have.

UPDATE: I tool the ALT off and pulled off the back plastic cover and a little silver screw fell out. I remember the moment now... I was teaching my son to work on cars and letting him change the plugs. I just started the little screw that holds the wire loop in place (presumably the ALT output wire) when my son asked me how to get the "coil wires" off. I turned and showed him how to remove the coil/boot assembly and turned back to the ALT. Everything was happily in it's place... just NOT tightened. I'm putting the ALT back in now. I'll update WHEN I've got it working perfectly. Any minute now...

Lesson for the day... DOUBLE and TRIPLE CHECK everything before you put it back in/together. Don't let ANYTHING distract you. I've only got one arm, so this stuff is hard enough without having to do it twice! I hope this helps someone else.

UPDATE 2: All done. Voltage hovering at 14.1V. Yeah! VERY QUICK job when you've already done it once!

Last edited by pcstan; 05-31-2011 at 10:22 AM. Reason: Update
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Old 06-01-2011, 03:59 PM   #75
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E46 forum much more active than E60 (2004+ 5-series)

Originally Posted by Girmis View Post
I am surprised this thread is still alive and kicking.... Too bad I sold my e46 and do not visit these forums often anymore. 5 series forums are dead compared to e46fanatics....
Agreed. I also have 530xi, in addition to my 325xi, but the 5-series forums are anemic compared to this one, although they too are useful. This forum is a beehive of activity.

e46fanatics has given me a tremendous amount of information and confidence. I now do everything myself. Reading the DIY posts here beat the stuffing out of Bentleys or Haynes.

Thanks to the thoughtful do-it-yourselfers for taking the time to share their experience.

I read this thread, deciding whether or not to replace my Bosch 120A alternator just as preventive maintenance. My 325 is at 122k and I don't want it failing in Yellowstone over a $50 component (voltage regulator/brushes assembly).

I wasn't looking forward to removing the alternator to replace the regulator and I'm very happy to find out that isn't necessary.
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Old 06-07-2011, 09:08 PM   #76
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I'll second, third, or fourth the thanks for the technical knowledge here. Having owned an Audi A4 for 14 years and 278,xxx miles, the 330xi my fiancee and I bought recently is a whole new thing now that I've started doing some work on it. Generally well thought out, and I'm impressed overall, but it's just different from the Audi.

Our battery light came on for the first time the other day, at high RPM only. After that it came on at startup once, then went off again. Following the advice here, including the knowledge that we'll likely be stranded if not handled quickly, I ordered a new VR, and replaced it today, without removing the alternator.

Now the battery light is on all the time. I wasn't hearing any noise from the alternator, so I was assuming I could get by with just the VR, but I guess I need to order a new alternator now. Anything else I should be considering?
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Old 06-08-2011, 04:21 PM   #77
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I have just changed the Voltage regulator on a 2002 325i with only 50k miles.

The car needed a jump started at the shop parking, the battery is almost brand new.... so why?
The measured voltage is only at about 10+ volts when engine was running...

I took out the alternator and brought it down to both Autozone and OReilly for a bench test.
They both showed my alternator is all dead. alternator failed, rectifier failed, VRegulator failed...

Anyway, bought the vRegulator online for $40, put it on. fixed the problem.
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Old 06-11-2011, 10:17 PM   #78
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Originally Posted by Rxmar23 View Post

Now the battery light is on all the time. I wasn't hearing any noise from the alternator, so I was assuming I could get by with just the VR, but I guess I need to order a new alternator now. Anything else I should be considering?
It's a little tricky trying to change the VR with the ALT in the car. Before buying a new unit, I would take the ALT all the way out and remove the VR cover and check for missing/loose screws and nuts. If the light is on all the time now then you probably missed something or left something unconnected. It's not likely that you got a bad VR. I hope all goes well.
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Old 06-13-2011, 08:14 AM   #79
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Well, as has been described here, I got the full light show on the way back from having the alternator tested ad Advance Auto. I made it home, up our big, 2 mile hill, but just barely. I replaced the alternator and that did the trick -- battery light went out right away, and the rest of the warnings went out after a few feet of driving. I put the old VR back on the core and kept the new one for the future.

I started on Thursday night, and got totally frustrated. The work recommended by the manual got increasingly greater (remove the cooling fan, shroud and radiator, to do that remove the bumper, to do that...), so I decided to give up and come look at the DIYs here. Unfortunately, it looks like most of the DIYers drive RWD manuals, where we have an AWD automatic, because things were different from what I was finding. Still, I got what I needed, I just had to look at a few different write-ups, for alternator and belt replacement.

I got it out on Friday night, but stopped there because we were getting beaten by a wicked thunderstorm. Found out the garage has a leak, right above where I was working, and the power hits we took while my arms were stuck down by the engine freaked me out, even though I knew I had disconnected the battery.

I had to remove the ATF reservoir, which is just 2 bolts, and very simple as long as you don't drop one. :-O I found there wasn't enough room to get my big adjustable wrench on the fan bolt, but I have a very flat 32mm bicycle headset wrench that did the trick. If any of you are cyclists and have this tool, no need to buy the special BMW wrench.

I suppose the various opinions on replacing the VR in the car or how hard it is to R&R the alternator depend on a lot of factors, from the size of your hands to what tools you happen to have (length of socket extensions, etc.). Someone mentioned a 5/8 socket for the fixed pulley, and that was just right, as my set doesn't have a 16 mm socket. I used a 5mm (IIRC) allen socket on the tension pulley, instead of a Torx -- I found it was easiest to move it with my hand, then hold it in position with the wrench. I couldn't have done the fan without the huge "Perfect Handle" screwdriver (passed down from my father) to wedge the motor side. No bending on that sucker.

Thanks to all of you for helping me through and saving me money. I'll be back for more, and hopefully can help someone else out myself someday.
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Old 06-17-2011, 12:29 AM   #80
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Originally Posted by Girmis View Post
Hello everyone,

I saved so much money working on my BMW and all thanks to e46fantatics! Thank you everyone for posting! I feel that I have to give something back to the community. So here is my first diy guide.

I searched this site, google, could not find how to change voltage regulator and brushes on e46. Decided to do it myself.

Initial problem was that alternator would give only ~10.3V if I had my lights and AC on. That drained my new battery. As my car is 2001 (06/2000 production), I decided that it was either brushes or voltage regulator. Ordered Voltage regulator (it comes with brushes) from pelicanparts, it is $53 (compared to $212+shipping on re manufactured Bosch alternator).

There is a good guide how to replace the alternator


so I won't repeat it. When you have your alternator out, there is a plastic back plate. You have to remove one screw (#3 in picture and two nuts (#1 an #2). #1 is under this rubbery plastic cover, use screw driver to pry it out.

After you remove the cover, you should find ..... this

I found all sort of stuff - leaves, paper, cigarette butts, you name it. The voltage regulator is connected with 3 screws and slides out after, no clips.
My old brushes were worn, but not to the extent that alternator would not work, one was shorter than the other one. Go figure...

The whole process takes about 10-15 minutes (after you have alternator out). It is cheaper that buying refurbished alternator and it is way cheaper than taking to the dealership. If you alternator does not make any noises (ball bearings) changing just the regulator will save you lots of money. I believe it is easier to do this than remove the pulley while switching alternators... After I changed the regulator, with long beams on, AC on it runs 13.6V to my battery, I believe that is within specs of 13.5 -14.5V. Maybe on the lower side, but hey, its not 10.3V like before.

I hope that helps someone.

Part number from pelikan $53 12-31-7-559-183-M14 link
Nice write up buddy. I had to read this like a bible when my alternator voltage regulator died last week. U did a marvellous job. The picture helped too.
Its simpler to remove the voltage regulator without removing the alternator, Thanks to your pictures.
Thanks for sharing
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